A silicon (Si)-deficient top soil was used in a pot experiment to investigate the effect of Si application on the shoot and root morphology of alfalfa (Medicago sativa L.). Silicon was applied to the alfalfa plants at 6 different rates (0, 0.025, 0.05, 0.10, 0.20, 0.30 g/kg), and each treatment was replicated 6 times. This study indicated that the Si content of roots and shoots increased significantly (P<0.05) with increasing Si concentration in the soil, and that the Si content of roots was greater than that of shoots. Plants treated with Si had increased leaf area, height, forage yield and shoots per plant during the reproductive period in comparison with controls. The application of Si also increased root volume, the number of secondary roots and root biomass. The effects of Si application were greater on roots than on shoots. The ratio of shoot to root dry weight was below 1.62 when Si was applied to plants and 1.91 without Si application. Overall, overcoming available Si deficiency resulted in a significant increase in shoot and root growth.

Forage yield and density are common selection criteria for assessing the suitability of lucerne varieties in high rainfall conditions and under irrigation. However, selection criteria for assessing the suitability of lucerne varieties is not well defined in dryland farming systems. This study combines forage yield, plant density, root biomass and proline content in the plant leaf to compare the suitability of 1 local and 8 introduced lucerne (Medicago sativa) varieties over 3 years in the dry environment of west China. The results of this study indicated that the above measurements significantly differed among the 9 lucerne varieties, and also showed that suitability of lucerne varieties varied based on different indicators. Ameristand 201 and Algonquin performed well in terms of forage yield. Ameristand 201 and Sandili were well-adapted varieties based on root biomass and Ameristand 201 was the first selected variety in terms of drought resistance. Combining initial establishment density and its decline over years indicated that Sandili maintained good persistence. A cluster analysis of 9 lucerne varieties indicated that Ameristand 201 was very suitable for sowing in the dry Loess Plateau, a high water-erosion region in west China.